LONDON — Brexit has driven advertising and marketing giant WPP to invest in France, Germany, Italy, and Spain, according to CEO and founder Sir Martin Sorrell.

Sorrell told Sky News on Wednesday morning: "The migration issue or the fluidity of people is really important to us. About 17% of the 14,000 or 15,000 people we have in the UK come from the EU. If there are severe restrictions on their movement, inward or outward, in the future, that obviously impacts our business in the UK.

"Our response to that has been actually to increase our investment in France, Germany, Italy, and Spain because those are four of our top ten markets and we can't afford to lose influence in those markets."

"The uncertainty is the killer," Sorrell said. "That's the cancer, the problem we have to deal with. The longer this goes on for, the more uncertainty the more issues it creates."

However, Sorrell added that WPP's recent performance in the UK has been good.

"Having said that, in relation to our own business... our business has been strong in the UK, in fact, it's been the strongest region for the last could of quarters," he said.

Sorrell was speaking to Sky News as WPP announced its half-year results, showing a tough start to 2017. The advertising and marketing holding company is forecasting revenue growth of 0% to 1% for the full year.

Asked about "Trumponomics," Sorrell told Sky News businesses were "bullish" about the President to begin with but that relations had faltered recently.